DIFFERENTIAL EXPRESSION OF THE BETA-I-PKC AND BETA-II-PKC SUBSPECIES IN THE POSTNATAL DEVELOPING RAT-BRAIN - AN IMMUNOCYTOCHEMICAL STUDY

Differential expression of protein kinase C subspecies, beta-I- and beta-II-PKC, derived from a single gene by alternative splicing was evidenced in the postnatal developing rat brain. Immunoblot analysis of the PKC subspecies in the whole developing brain showed that beta-I-PKC was present at birth and then gradually increased, while beta-II-PKC was not present at birth or on postnatal day 3, then increased rapidly from day 7 to the maximum value seen in the adult brain. Under light microscopy, beta-I-PKC immunoreactivities seen at birth were the most intense in the brainstem and intense in the diagonal bundle and globus pallidus. Beta-I-PKC immunoreactivities in these neurons weakened from day 7 and disappeared in the adult brain, while in the cerebral cortex, triangular septal nucleus and pontine nucleus beta-I-PKC immunoreactivities were weak at birth and then gradually increased. Beta-II-PKC immunoreactivities were first visible in neurons on day 7 and increased progressively. beta-I- and beta-II-PKCs were not co-localized in a neuron, as far as examined. The immunoreactivities of beta-I-PKC at birth were localized in growth cone-like structures as well as in the dendrites and perikarya. Similarly, alpha-PKC was also present at birth in the growth cone-like structure. Immunoblot analysis revealed that beta-I-PKC was present at birth in the growth cone-rich fraction from the hindbrain but not in that from the forebrain, while alpha-PKC was found in the growth cone-rich fraction from both the forebrain and the hindbrain. Beta-II- and gamma-PKC were not detected in the growth cone-rich fraction from either forebrain or hindbrain. These findings suggest that beta-I- and beta-II-PKC play a role in different stages of development and in different neurons; both beta-subspecies may be involved in postnatal developing neuronal functions while only beta-I-PKC plays functional roles in the growth cone, in the prenatal developmental stage.